Iron ore contains 30 to 70% iron (Fe), and good-quality iron ore is small in the amount of hazardous components such as sulfur (S), phosphor (P), and copper (Cu) and uniform in size. However, the iron ore produced in an original place is not uniform in components thereof and thus cannot be directly put into a blast furnace. Generally, the iron ore is charged into the blast furnace as a sintered ore by making the components thereof uniform, mixing the resultant iron ore with corks and sintering the same.
FIG. 1 illustrates a general method of manufacturing a sintered ore.
That is, as shown in FIG. 1, various kinds of iron ore as a major material of the sintered ore and silicastone, serpentinite, and limestone as a minor material, and stone coal and corks as a fuel are transferred from a storage bin 110 through a conveyor to a mixer 120.
Also, the material, fuel, and ores are mixed together in the mixer 120 and granulated with moisture added thereto, and then fed to a surge hopper 130.
Then, the surge hopper 130 supplies sintering materials fed from the mixer 120 to a sintering trolley 140 at a predetermined ratio. Sintering materials are supplied first by an upper ore hopper 150 installed behind the surge hopper 130 to be sintered before the sintering materials stored in the surge hopper 130 are supplied.
Moreover, an ignition furnace 160 disposed before the surge hopper 130 ignites an upper portion of the sintering materials on the sintering trolley 140. The ignited upper portion of the sintering materials is sintered together with a lower portion thereof by virtue of a suction force of a wind box 170 including an air exhauster 172 and a chamber 174 below the sintering trolley 140.
Then, the sintered materials are transported forward along the sintering trolley 140, thrown into a cooler 180 to be cooled in air, and then manufactured as a sintered ore.
Thereafter, the sintered ore produced is crushed by a crusher 190. The crushed sintered ore is separated into a return ore (sintered return ore) with a grain size of 6 mm or less and a sintered ore with a greater grain size by a hot screen 200.
For example, the sintered ore with a grain size of 6 mm or less is not sent to the blast furnace 210, but returned to the sintering process. Such a sintered ore is generally referred to as a “return ore”.
That is, the sintered ore usable in the blast furnace has a grain size of about 6 to 50 mm, and thus the sintered ore with a grain size of 6 mm or less is re-thrown into the surge hopper 130 as indicated with line A of FIG. 1.
Meanwhile, even though not illustrated in detail in FIG. 1, the sintered ore having a grain size (diameter) of greater than 6 mm is cooled and then crushed at a predetermined ratio by a cutting feeder. Also, the sintered ore with a diameter of 50 mm or more is crushed up to 50 mm, which is a size allowing the sintered ore to be charged into the blast furnace. The sintered ore is finally put into the blast furnace 210 through several sorting processes using a screen, as indicated with line B of FIG. 1.
However, typically, the return ore having a grain size of 6 mm or less accounts for a considerable proportion, i.e., about 40% of the sintered ores generated in an actual sintering process. But such a return ore can not be directly charged into the blast furnace to ensure permeability and is subjected back to the sintering process.
Therefore, the return ores (sintered return ores) may be agglomerated (fusion-bonded) to a grain size (diameter) of greater than 6 mm to be charged into the blast furnace. This accordingly precludes a need for a process of re-treating the return ores, which requires the return ores to be subjected back to the sintering process.
Meanwhile, to agglomerate the return ores to a grain size of greater than 6 mm, a question of how to physically bond (fuse) the return ores should be solved. There are sane known methods to be considered as follows.
To begin with, the return ores may be bonded using a binder, which is a median for bonding the return ores. With this binder, the return ores can be advantageously bonded in a cooling state without a need for pre-heating the return ores. However, disadvantageously, the binder for bonding the return ores is typically weak to heat and lost when put into the blast furnace. Thus, the agglomerated return ores are very likely to be broken into small grains in the blast furnace.
Next, a commercially viable laser may be employed. However, the laser is capable of fusing a very small effective area (radius) of the return ores, thus not productively feasible when fusion-bonding the return ores. Besides, an actual test found that the return ores are weakly bonded by the laser.
Another alternative method involves thermal spray welding, in which spray power is sprayed onto an object to perform welding. In this case, the return ores are excellently bonded but the spray powder adversely affects molten iron components in the blast furnace process, thus hardly applicable in practice.
Finally, an ultrasonic metal pressing for bonding non-iron metal and plastic may be adopted. In the ultrasonic metal pressing, a friction force is generated on contact surfaces due to vibration to thereby bond the return ores. However, the bonded return ores have rough surfaces and may be fractured by a predetermined pressure imposed.
Thus, the applicant of the present invention has cane to suggest a technology for agglomerating the return ores through more effective fusion binding. This technology allows the return ores to be agglomerated with a uniform size and the sintered ores to meet quality standard. Particularly, with this technology, the return ores remain strongly bonded even after fusion binding, posing no difficulty to a process flow until the return ores are charged into the blast furnace and the return ores can be treated in a massive amount.
Meanwhile, only sintered return ores have been described as an example of the return ores. However, the method of treating return ores of the present invention may be applied to other ironmaking process such as commercially viable FINEX or COREX which has overcome problems associated with manufacturing costs in sintering ores and environmental pollution in the blast furnace process, using non-coking coal and iron ores.
The present invention has been made to solve the foregoing problems of the prior art and therefore an aspect of the present invention is to provide a method and apparatus for treating return ores using plasma, capable of fusion binding and agglomerating the return ores to a predetermined grain size using a flame of a plasma heating device.
Another aspect of the present invention is to provide a method and apparatus for treating return ores using plasma, in which the return ores can be treated in a massive amount to enhance productivity of agglomerating the return ores through fusion-bonding and also a great amount of sintered return ores generated in the sintering process are subjected to a fewer number of re-treatment processes.